In the returnless regulator system set forth in U.S. Pat. No. 5,413,077, of common assignee herewith, a fuel pump supplies a flow of fuel to a pressure regulator adjacent a fuel rail at a constant flow rate for all fuel demand modes, i.e., at all engine or vehicle speeds. The system fuel pressure provided by the fuel pump is maintained at a slightly higher pressure than the pressure in the fuel rail. The function of the returnless regulator is to reduce the pressure supplied by the fuel pump to the predetermined regulation pressure which enables the fuel pressure in the fuel rail and the fuel injectors to deliver the correct amount of fuel to the engine. Thus, the lower fuel rail pressure is determined by the returnless regulator, while the slightly higher system pressure is determined by a pressure relief valve carried within a fuel pump module located with a fuel tank. This enables the pressure regulator to be mounted on the fuel rail closer to the engine as compared to other non-return fuel systems in which a regulator is mounted in the fuel tank. The pressure relief valve enables the excess fuel to be returned to the fuel pump module without a fuel return line from the returnless regulator to the fuel pump module or fuel tank. Also, the returnless regulator can be optionally vacuumed referenced to the intake manifold so that a constant differential pressure across the fuel injectors can be maintained.